This invention relates to an injector for use in supplying fuel at high pressure to a cylinder of an associated internal combustion engine, in particular to an injector in which the injection pressure and timing of injection can be controlled independently.
One technique for controlling injection pressure independently of injection timing is to provide an injector arranged to be supplied with fuel by a suitable cam operated pump, which conveniently forms part of the injector, the injector including a first valve arranged to control the flow of fuel to a suitable low pressure drain, and a second valve arranged to control the movement of a valve needle of the injector. It will be appreciated that the second valve controls the timing of the start and end of injection, whilst the injection pressure is controlled by controlling the time at which the first valve closes relative to movement of the second valve; higher injection pressures being achieved by closing the first valve early compared to the timing of commencement of injection. The first and second valves are controlled independently of one another thus the injector and control arrangements for the injector are relatively complex.